Note: UDP is the default interconnect protocol for RAC, and TCP is
the interconnect protocol for Oracle Clusterware.
Token-Ring is not supported for the interconnect.
At the time of this release, Hyper-Messaging Protocol (HMP) is not
supported.

Selon Sriram Kumar :

Hi Gurus,

We are presently using a HP Itanium2 cluster running Oracle 9i RAC. We are
to migrate soon to 10g RAC. Was surpised to find a note in metalink that
says that HMP is not supported in Oracle 10g RAC. Note id 220970.1

Is HMP supported with 10g on all HP platforms ?

10g RAC + HMP + PA-RISC = yes

10g RAC + HMP + Itanium, "Oracle has no plans and will likely never
support RAC over HMP on IPF."

When we migrated to Oracle9i RAC, we were said (rather pushed) that
HMP would be much better that UDP and we bought expensive HyperFabric
switches and now Oracle cooly says HMP is not supported now we will
have to run UDP on these HyperFabric switches

Thought this would help others in the list using HMP or planning to
buy Hyper Fabric